James Sunderland encounters either Mary Shepherd-Sunderland or Maria in the game's final scenes (in the form of Mary), depending on the player's actions throughout the game. If Maria, he rejects her and this causes her to transform. If Mary, she blames him for her death and proceeds to attack James, initiating the final boss fight.
She appears as a version of Mary's corpse splayed in a metal frame, similar to the Flesh Lip. Her arms and legs end in a series of short tentacles rather than hands or feet, and she is suspended in the metal frame, screaming and upside-down.
Mary attacks by spewing forth a swarm of moths from her mouth in order to injure and delay James, as the insects are flesh-eaters. She can also hit James with the frame she rests in or use her tentacle to strangle him, provided that he is within range. She takes quite a bit of damage before falling, so saving up ammunition for the encounter would be recommended, though it is not necessary; she eventually falls herself. It is very difficult to attack her with a melee weapon due to the metal frame and tentacles she uses. The rifle is the best choice to fight her with. After she falls to the ground, she whispers James's name repeatedly. One last blow to the now-helpless monster ends the fight.
According to the Book of Lost Memories, Mary's form represents James's conflicted emotions towards her during her final days. The metal lattice probably symbolizes Mary's sense of confinement in being bedridden due to her illness, while the moths that surround her are used to symbolize death; comparatively, Maria has a tattoo shaped like a butterfly, which represents rebirth. Ironically, Mary can also use the tentacle to strangle James, similar to his asphyxiation of her.
- Defeating Mary in the Silent Hill HD Collection awards the trophy/achievement "Say Goodbye".
- Mary is one of the only five monsters that are conscious and can speak in their monstrous forms, the other four being Leonard Wolf, Momma, Steel Guardian, and Monocle Man. Note that the Sad Daddy could speak only in its human manifestation.
- Mary makes a cameo in Silent Hill: Shattered Memories. She can be seen floating in the corner of Dr. Kaufmann's office during the UFO ending.